This invention relates generally to fiber optic connectors, and more particularly, to a fiber optic connector for coupling a pair of fiber optic cables or a single fiber optic cable and a light source or detector in a separable in-line connector. More specifically, the invention relates to a fiber optic connector of the type which when assembled requires no epoxy to hold the fiber of a fiber optic cable and permits flush cleaving of the fiber with the termination end of the connector to avoid the requirement with most prior art connectors of polishing the end of the fiber.
It is generally known in the industry that a fiber optic cable generally includes an optical fiber surrounded by a coating or "jacket", with strength members extending longitudinally between the optical fiber and the outer coating or jacket. The strength members are typically made of fiber material sold by DuPont under the name Kevlar.RTM.. An optical "fiber" conventionally includes a core surrounded by a cladding, both of which are of glass but with different indices of refraction. However, in the specification and claims herein the terms "core" or "fiber core" or "waveguide" will be used to denote this composite element of the fiber optic cable unless otherwise indicated. In addition to the above, surrounding the core or waveguide is a buffer layer typically made of silicone which is intermediate the strength member layer and the core of the cable.
The terminal end surface of an inner fiber core of a fiber optic cable for use in light wave transmission must be flat and highly polished to minimize insertion losses. In addition, the fiber must also be axially, laterally and angularly aligned within certain tolerances to establish good optical coupling between two cables, or a cable and a sensor or a light transmitter.
Typically, in the prior art, there have been developed many fiber optic connectors which are precision, expensive instruments providing very low insertion losses. These connectors are typically designed for certain applications such as long distance applications in telephonic systems and in other applications requiring extremely low insertion losses where expensive low loss connectors may be employed. On the other hand, expensive low loss connectors are not always well suited for applications which require a large number of connectors which, as a result of their high cost, makes the use of these connectors not economically feasible.
Examples of such applications not suited for expensive connectors are computers, cable television and other data tranmission applications, which require that a large number of fiber optic cables be employed. Thus, there is a need for low cost, low loss fiber optic connectors which minimize insertion losses due to off-centering of the fiber relative to the outer dimensions of the connector or terminal member. In the case of most prior art low cost fiber optic connectors, although cost is reduced, excessive insertion losses result due to, for example, the inner fiber core often being not concentric with the outer coating or cladding which leads to excessive insertion losses when a connector that utilizes the outer coating or cladding as a jigging surface is put into a data transmission line.
U.S. Pat. No. 4,515,434 having a common inventor with the inventor of this device, discloses an improved low cost fiber optic connector for optically coupling a pair of fiber optic cables, or a single fiber optic cable and a light source detector which avoids a number of the above-discussed disadvantages. More particularly, a terminal member is provided having a through-hole extending axially therethrough including a portion of the through hole sized to snugly receive a length of fiber. A clamping arrangement is provided in the back portion of the elements defining the through-hole for clamping the outer coating of the cable to prevent lengthwise movement of the fiber optic cable relative to the terminal member. In this manner, all the elements of the fiber optic cable are securely held and due to the precise molding of the connector, it is possible to precisely align the connector to another connector or sensor or light source.
On the other hand, the connector of U.S. Pat. No. 4,515,434 includes a number of disadvantages in that it is of different shape from standard connectors known as SMA connectors and thus, are not compatible. Further, the clamping member for the cable does not always ensure tight clamping and there is the possibility that, due to the multiple layers of the cable, some movement is still possible with respect to the cable and therefore, the fiber can be brought out of alignment or moved longitudinally within the connector itself.
A still further disadvantage is that the connector is made of two parts and to ensure non-longitudinal or transverse movement of one part with respect to the other, a relatively difficult to mold pin and hole arrangement is required to ensure that the two halves are retained together and further, there is reliance on an adapter to hold the halves together, which holding or securing of the halves together is not effected until the entire arrangement is coupled to a like connector or sensor or light source.